Soooo... 1) using 5w30 as the example, people argue over whether KV100 10cst is better or worse than 9cst (or 9.2 is better than 8.2 in a UOA). KV40 specs are sometimes on PDS's, but we rarely see them on VOA's or UOA's, but in general, to continue with 5w30 example, are generally between upper 50's to 70 (a numerically wider spread than 8 to 9, or even 10). We never see 0C KV spec's do we? Seems 0C would be a useful number, more relevant than -40C specs, except for those poor souls who have to start their engines in N. Dakota winter. But look at how big those visc numbers are at pour point. Us newb-mere-mortals can't even comprehend the difference in the typical numbers. As pointed out above, some 0w30's are "thicker in the middle" than 5w30's, though don't hit the wall at sub-sub-sub freezing Arctic temperatures. It would be nice to know oil specs for 0C, then some some mid-point (and I dont have a problem with 40C), then the "normal" engine temp of 100C. And I don't mean we should take away the readings useful to the Dakotans. 2) taking it the other direction, I've read arguments over HTHS readings of 3.5 or "better" vs 3.1 or "worse." Numerically, a small difference. But seems safe to say, when the "normal engine temp" is 100C, the oil temp in a turbo, or even a main bearing, might be significantly higher. So the closest surrogate I've seen is the HTHS number, but really, how much better is 3.5 compared to 3.1, or 2.9? What delta is really considered significant here? 3) obviously, synthetic vs conventional designation has been smeared so badly, only a handful can make sense of the outlandish performance claims. Thanks to the poster above for explaining how grIV might need less VI treatment than a grpIII, and I guess that was meant to say the grpiV would shear less. But not all synthetics are grpIV.ðŸ™ 4) I get the sense, a fair number of people think "modern" oils are less protective than certain older specs (and I don't mean 1970's specs, but say, recent 10w30, 0w40 or 5w40 vs "government-mandated" or government-encouraged 0w20's. Conversely, some equate SN+ to nirvana. Someone comment on how a newb-mere-mortal, such as myself, can differentiate oil quality. And the first person who says, "just use what's in the owners manual," gets the sit-down-and-shut-up buzzer, because that helps no one understand. I love clean air, and non-polluted environments, but for the moment, can we take fuel-economy out of the discussion, and focus on wear protection? Well, it's OK to discuss deposits, varnish, and sludge. For the record, both my vehicles have turbos, and lots of rants about how hard they are on oil (especially the Subaru). But you can find my Ford UOA's, and I don't remember anyone saying, "Gee that ILSAC GF5 GrpIII+ Synthetic sure did great." So I tried the Valvoline PBRestore, and people DID say "gee, that oil did great" but I have no intention of making that my regular fill. Can't afford that, although cheaper than an engine tear down. So still searching for the affordable unicorn oil.